In the last post, I wondered whether rerouting the downspout drainage away from the house would be enough to avoid more flooding… Well, I decided that it was better not to take any chances, so I started digging. I’d already dug a little hole to check for drainage pipes, so it was just a matter of continuing. Lifting rocks isn’t exactly my strong point, so I’ve been doing it in small increments (all the while hearing the song “16 tons” in my head) but I’ve made it basically along the entire front of the house.

It’s been pretty dry for the past month or so, but the other day we finally got a good Hilo-style rain of something like 5″ of rain over 12 hours. That at least answered the question of whether doing all this digging was necessary, because when I checked it out in the morning, it looked like this:

Water pooling in the trench next to the house

After admiring all that rock I’ve hauled out of the ground, you probably notice that the bottom of the trench is filled with water! When I first discovered it, the water was more than a foot deep. Nothing had yet made it into the basement, but I wasn’t about to wait and see. After a quick trip to Home Depot to get a pump, I started pumping the water out.

The pump, which is supposed to pump 1500 gallons/hour, barely kept up with the incoming water when the rain was heavy.

First, the pump barely kept up with the incoming water, then the rain got heavier and it lost ground. The water level rose so it submerged the entire pump for a while, then it largely stopped raining and it made some progress. It took until late afternoon until all the water was gone. As the water level dropped, I could actually see water flowing out through the rocks under the house and into the pool!

I think what’s happening is that the whole yard is basically made up of a fill of these large lava rocks, lying on top of solid lava at some point. The rock fill is very porous, so the water will flow down the slope on top of the solid lava until it hits the house, where the concrete footing basically makes a dam which the water fills up.

As you can see in the pictures above, the water filling the trench is absolutely clear. It’s clearly not flowing through dirt. Whatever material it’s going through on the way has probably been washed clean over the years, which is good because it seems the risk of getting the drains clogged with silt will be minimal.

The drainage situation probably isn’t improved by the fact that the street facing the yard has no gutters. When it rains heavily, water comes streaming down the street, running off the side facing our yard. The neighbors’ yard is also higher than ours on the street side, so water probably also flows down that way. Maybe adding a surface drainage along the street would help? But first we gotta get the drainage around the house down. I’m almost down to a good level along the top side of the house, but there are some very large rocks that still need to be removed or cracked off so the drainage pipe can maintain a good slope. Then we need to get the pipe down along the side, too…